The past year of this project focused on PET studies of behaviorally characterized aged (19 years<) rhesus macaques and of aged animals that are part of an ongoing study of gene therapy in the central nervous system. We combined these two specific aims into a single series of pet studies utilizing the tracer 2-(18f)-fluoro-deoxyglucose (FDG18) to determine regional metabolic rates for glucose (RCMGLC) as in the first year of our study. The study population consisted of six aged (19 years <) rhesus macaques. These animals completed both MRI for slice selection and PET scans utilizing FDG18, then underwent behavioral assessment followed by intracerebral grafting with genetically modified fibroblasts as described in the project "transgene therapy in Alzheimers disease. " The target of the grafting was the nucleus basalis of meynert. Grafted cells consisted of autologus fibroblasts containing the human gene for nerve growth factor. Three animals were grafted with NGF cells and three with cells containing the gene for B-galactosidase. The grafted animals were studied prior to surgery and approximately 2 months after the surgical implantation of either NGF or control grafts. The non-surgery control animals were studied at two different time points, with approximately 2 months between the first and second scan. Both the NGF animals and the grafted control animals showed increased relative metabolism in the temporal cortex when compared with the non-surgery controls. Additionally, relative metabolic rates in the orbitofrontal cortex appear to increase for both NGF animals and grafted control animals, although slightly more for the NGF animals. Increased metabolism in the neocortex may be partly due to a surgery effect, while increases observed in NGF animals may reflect both a surgery effect and specific effect of the NGF graft. CRPRC administration:2a3 primate services.